This effort presently has and is constructing models of cardiac metabolism in the rat heart (perfused) and the dog heart (mostly in situ). Emphasis is on glycolysis, the Krebs cycle, and transport between cytoplasm and mitochondria, with growing attention to cell membrane transport, and with ischemic rather than normal hearts. Particular attention will be given to fatty acid oxidation, loss of adenine nucleotides from ischemic tissue, management of glycogen reserves, etc., and to further development of the models. Related technical improvements -- in building and applying such models more quickly and economically -- are also expected.